Recycling of waste materials is highly desirable from many viewpoints, not the least of which arc financial and ecological. Properly sorted recyclable materials can often have significant monetary value. Many of the more valuable recyclable materials do not biodegrade within a short period, and therefore properly recycling these materials significantly reduces the strain on local landfills and ultimately the environment.
Typically, waste streams/mixtures are composed of a variety of types of waste materials. One such waste stream is generated from the recovery and recycling of automobiles or other large machinery and appliances. For example, at the end of its useful life, an automobile will be shredded. This shredded material can be processed (by one or more large drum magnets) to recover most of the ferrous metal contained in the shredded material. The remaining materials, referred to as automobile shredder residue (ASR), may still include ferrous and non-ferrous metals, including copper wire and other recyclable materials such as plastic.
ASR is mainly made of non-metallic material (dirt, dust, plastic, rubber, wood, foam, etc.), non-ferrous metals (mainly aluminum but also brass, zinc, stainless steel, lead, and copper) and some remaining ferrous metal that was not recovered by the first main ferrous recovery process (that is, the drum magnets). Recently, efforts have been made to recover additional materials from ASR, such as non-ferrous metals and plastics. Similar efforts have been made to recover white goods shredder residue (WSR), which are the waste materials left over after recovering ferrous metals from shredded machinery or large appliances. Other waste streams may include electronic components, typically referred to as electronic scrap, building components, retrieved landfill materials, waste incinerator ash-referred to as bottom ash, or other industrial waste streams. These materials generally are of value when they have been separated into like-type materials.
However, cost-effective methods are not available to effectively sort waste streams that contain diverse materials, especially when the waste stream contains materials with a number of diverse sizes, densities, shapes and moisture content. This deficiency has been particularly true for non-ferrous materials, and especially non-ferrous metals, including insulated copper wiring, and for non-metallic materials, such as high density plastics. This combination of diverse materials and diverse material sizes, densities, shapes and moisture content present a unique challenge in separating and recycling specific materials in an efficient manner.
Conventional known systems to concentrate or recover recyclable materials, specifically non-ferrous metals from waste streams, typically employ a first step composed of a screening device, such as a vibrating screen, rotating drum screens or star screens, which sort materials into similar size fractions. The term “screen” as used herein is intended to include any mesh-like sieve or grid-like device or perforated structure used to separate particles or objects. Long and thin pieces of metals, such as copper wire and stainless steel bars, present a unique challenge in screening materials from a waste stream because of the shape of such recyclables. Known screening processes other than a star or disc screen, such as vibrating screens or rotating drum screens, typically do not concentrate long and thin pieces of recyclables into one of the size fractions because of the three-dimensional shape of such recyclables. In some instances the long-thin recyclables can pass through the screen opening, but in other instances their length causes long-thin recyclable to remain on top of the screen. Once the recyclables have been screened into discrete size ranges, typically another step of conventional known systems to concentrate or recover recyclable materials may include an air separation apparatus that sorts the recyclables by their density into a light and heavy fraction.
Such screening and sorting technologies are typically implemented in two separate steps of the recycling or sorting processes thereby increasing their footprint, capital expenditure, and operating expense. In addition, they are limited in their ability to sort face sorting long and thin pieces of recyclable materials at high capacities and in a cost-effective manner. Moreover, high moisture content recyclables present a challenge during a typical screening and aspiration operation. The high moisture recyclables tend to block or clog the conventional screen's open area and when aspirated the high moisture recyclables tend to stick to each other, hampering the aspiration process.
Accordingly, there is always a need for improved processes and systems for sorting material. It is to this need that that this disclosure is directed.